This research is directed toward improved speech reception for users of hearing aids through a program of basic and applied research. Our basic research includes theoretical and experimental work concerned with developing an improved understanding of the role of the slowly varying envelope cues and the more rapidly varying temporal fine-structure cues of the speech signal. In particular, this research attempts to understand the factors that are responsible for the reduced ability of hearing-impaired listeners to understand speech in temporally-modulated noise and to make use of information carried in the temporal fine-structure of speech. The theoretical work will employ neural models of hearing loss for coding of envelopes and temporal fine-structure as well as perceptual models of the integration of these cues in order to develop an improved understanding of the source of these difficulties. The experimental work includes studies of the speech-reception abilities of listeners with normal hearing, sensorineural hearing impairment, and simulated hearing loss using speech signals that have been processed to convey various types of envelope and temporal fine-structure cues in backgrounds of steady-state and fluctuating noise. Performance on the speech tests will be correlated with a set of psychoacoustic tests that include measurements of auditory critical bands, pitch perception, and cochlear compression. These experimental results are important not only in developing a deeper understanding of the role of fine-structure cues in hearing-impaired speech reception, but also provide basic data for use in the theoretical modeling work and in our applied research concerned with developing signal-processing schemes for improved speech reception in noise. Based on our theoretical and experimental findings, we plan to develop signal processing strategies that aid hearing impaired listeners in backgrounds of interference. PUBLIC HEALTH RELEVANCE: This research is concerned with the development of improved hearing aids for people who suffer from hearing impairments that cannot be treated medically. One of the greatest difficulties faced by listeners with sensorineural hearing impairment involves understanding speech in backgrounds containing interfering sounds. The proposed research is concerned with an improved understanding of the poor performance of hearing-impaired listeners in noisy backgrounds and the development of signal-processing methods to remediate these difficulties.